Have you used a "Totals Query" - if not, check it out because I think it will accomplish exactly what you want.
Assuming each production run has an index (if not, add one), then you set your query up to "Group By Production Line", "Order By Run Date/Time" and to "Show Last Index"
The result is a list of the index value for the most recent run of each production line. You add that to a Select Query to add all the human readable stuff like the name of the production line, etc. and you're in business.